ANIMAL BEHAVIOR

ANIMAL BEHAVIOR

Introduction to Ethology

I. Definitions

A. Behavior

B. Ethology

II. Levels of Investigation

A. proximate factors

B. ultimate factors

III. An Evolutionary Approach to Behavior

A. Review of Evolutionary theory

1. Evolution

2. Natural selection

3. Example: infanticide in lions

B. Characteristics of natural selection

1. units of selection

2. different behavioral strategies

3. anthropomorphism

Neurological Basis of Behavior

I. The Neuron

A. Morphology and types

B. Membrane properties

1. resting neuron

2. action potential

C. The synapse

1. electrical synapse

2. chemical synapse

a. functional types

b. transmission ratios

c. integration within neurons

II. Stimulus-Response Relationships

A. General Considerations

B. Classical ethological view

1. an example: egg retrieval in greylag goose

2. ethological model

a. sign stimulus

b. innate releasing mechanism

c. fixed action pattern

C. Neurological Mechanisms

1. stimulus recognition

a. ticks

b. feeding in gull chicks

c. advantages and disadvantages of sign stimuli

2. decision making

a. startle behavior

1) example: crayfish tail flip

2) neural circuitry and command neurons

b. evasive behavior

1) example: evasion of bats by noctuid moths

2) neural circuitry

3. motor output

a. example: walking in the cockroach

b. central pattern generator (CPG)

c. interaction of CPG and sensory feedback

1) cuticle stress receptor of cockroach

2) walking and jumping in grasshopper

d. command centers and the organization of CPGs

1) praying mantis

2) honey bee sting

Navigation and Migration

I. Orientation with landmarks

II. Orientation without landmarks

A. Compasses

1. sun compass

a. honeybees: "marathon" dances

b. pigeons: displacement experiment

2. polarized light

3. stellar compass

4. magnetic compass

5. backup systems for compasses

B. Maps

1. genetically determined maps

a. displacement experiments: European stork

b. hybridization experiments: European black cap warblers

2. non-genetic maps

Time-shift experiment in pigeons

experimental set up: pigeons maintained in windowless room on 12:12 L:D cycle. Lights come on at 12 midnight and go off at 12 noon. After several weeks, transport pigeons 50 east of the loft and release them at 12 noon.

Actual Time

“Pigeon Time”

Actual position of sun

Where pigeons “think” sun is

12 midnight

6 AM (sunrise)

---

East

12 noon

6 PM (sunset)

South

West

results: Because of their internal map sense, pigeons know they have been taken east and need to fly west to get home. At 12 noon, the sun is in the south, but because the pigeons have been time shifted by 6 hours, their internal clock tells them it is 6 PM and thus they “think” the sun is in the west. They will therefore fly toward the sun to get home, when in reality they should turn 90^o to the right of the sun to fly west and get home.

Factors that Change Stimulus-Response Relationships

I. Concept of Response Threshold

II. Genetics

A. Mating and sexual behavior

1. Vasopressin 1a Receptor gene (V1aR) and pair bonding in voles

2. fru gene and sexual orientation in Drosophila

B. Maternal behavior: Glucocorticoid receptor gene and parental care in rats

C. Social behavior

1. foraging (for) locus

a. Drosophila

b. honey bees

2. Gp9 gene in fire ants

3. 5-HTT in humans

II. Endogenous rhythms

A. Example: daily activity patterns in the cricket singing

1. “classical” experiment

2. terminology

a. biological rhythm

b. biological clock

c. zeitgeber

d. entrainment

e. free run.

B. Clock mechanisms

1. per gene

2. mechanism in insects

3. mechanism in mammals

4. clock mechanism and command centers: mammals

a. PK2

b. entrainment

5. adaptations of clock mechanism

a. honey bees

b. naked mole rat

IV. Hormones

A. Priming effects

1. courtship and nesting in ringdoves

2. division of labor in honey bees

a. juvenile hormone (JH)

b. behavioral acceleration

c. behavioral reversion

d. social regulation of JH titers

B. Organizing effects

1. experiments on rats

2. mechanism of operation

Chromosomal Sex	Treatment as Neonate	Treatment as Adult	Sexual Behavior as Adult
XY	none	castrate	none
XY	none	castrate + testosterone	male
XY	castrate + testosterone	testosterone	male
XY	castrate	testosterone	female
XX	testosterone	none	male
XX or XY	castrate + excess estrogen	Testosterone or estrogen	male

V. Social Interactions

A. Mother-infant interactions

B. Play behavior

1. characteristics of play

2. functions of play

VI. Learning

A. Restricted learning programs

B. Semi-restricted learning programs

1. imprinting

2. song learning in birds

a. background information

1) development

2) functions

3) sonographic analysis

b. "classical" experiments

c. neurological basis of song

1) song learning

2) song production

d. updates on song learning

1) what can be learned?

2) plasticity of sensitive periods

a) photoperiod

b) social factors

3. language learning in humans

C. unrestricted learning programs

D. costs and benefits of learning

Foraging Decisions

I. Cost-Benefit Analysis and Optimality Theory: ex. crows foraging on whelks

II. Currencies for Measuring Benefit Gains

A. Maximize energy gain: ex. crows

B. Minimize costs: ex. Sunbirds

C. Maximize rate of food delivery: ex. Starlings

D. Maximize energetic efficiency: ex. honeybees

III. Constraints on Foraging Behavior

A. Handling time

B. Predation

C. Competition

D. Dietary needs

E. Energy budgets

Data Tables

II.

B. Minimize costs: ex. Sunbirds

Net engery No. flower in Hours spent Hours spent

gain/day territory foraging defending

Predicted

E max. 28-48 kcal 6300-9600 5.7-8.1 1.9-4.3

C min. 0 kcal 1540-1600 1.7-2.6 0.2-0.4

Observed -0.16 kcal 1600 2.4 0.3

III. Maximize rate of food delivery: ex. Starlings

Relationship of load size to distance traveled

20s 40s 60s 100s

Predicted 4 5 5 6

load size

Observed 3.9 4.8 5.3 5.9

load size

Communication Behavior

I. Definition of communication

II. Communication Model

A. Receiver

1. detecting the signal

2. signal meaning and the role of context

B. Sender

1. the message

a. internal referents

b. external referents

2. the signal

a. what cues become signals?

1) conflict behavior

2) others

b. the process of signal evolution

1) ritualization

2) emancipation

3) combination of 1 & 2

C. Channel of Transmission

1. olfactory channel

2. visual channel

3. auditory channel

4. tactile

III. The Use of Information in Communication (ultimate function of animal signals)

A. Cooperation vs. Manipulation

B. "Deceit" in animal communication

1. bluffing in mantis shrimp

2. withholding information

C. The evolution of "honest" signals

D. Modulatory communication

Constraint

Olfactory Channel

Visual

Channel

Auditory Channel

Tactile

Channel

Environment

Day or night;

Dense vegetation

(influenced by wind)

Primarily in daylight; open areas

Day or night;

Most habitats

Requires close proximity; short-range communication

Amount of Information that can be Sent

Low

High

Low (?)

Speed of Transmission

Slow

Rapid

Persistence of Signal

Moderate-High

Low

Ease of Locating Sender

Difficult

Easy

Energetic Costs of Signal Production

Low

Low-High

High

Low

Risk of Predation and Exploitation

High

Low

Resource Defense and Group Living

I. Dominance hierarchies

A. definition of dominance

B. factors favoring dominance

C. consequences of a dominance hierarchy

D. maintenance of dominance status

II. Territoriality

A. who defends?

B. when and how much to defend? (the concept of economic defensibility)

1. factors that influence defense decisions

2. example: Sanderlings

C. functional types of territories

1. breeding

a. impact on male reproductive success

b. consequences of competition for breeding territories

2. feeding

3. predator protection

4. display sites

5. future benefits

D. how to assess territory quality?

1. direct assessment

2. indirect assessment

III. Group Living

A. Advantages

1. reduced predation

2. increased foraging efficiency

3. increased resource defense

4. improved care of offspring

5. kinship benefits

B. Disadvantages

1. increased conspicuousness

2. increased competition

3. increased risk of disease and parasites

4. reduced reproductive success

C. Sunfish: a composite example

D. Group size: ex. Yellow-eyed Juncos

Mating Behavior

I. Sexual reproduction

A. why do it?

B. why have different sexes?

C. consequences of having separate sexes

1. differences in parental investment (PI)

2. different reproductive strategies

3. sexual selection

II. Sexual Selection

A. Intrasexual competition

1. factors influencing the degree of competition

a. inequality in PI

b. operational sex ratio

c. distribution of females

d. sperm precedence

2. mechanisms of competition

a. reduced threshold for arousal

b. male aggression

1) contested resources

2) evolutionary consequences of male aggression

a) sexual dimorphism

b) “honest” signals

c. sperm precedence

1) modification to male reproductive tract

2) mate guarding

3) repeated or prolonged copulation

4) mating plugs

5) toxic chemicals

3. evolutionary consequences of male-male competition

a. sexual dimorphism

b. “honest” signals

c. alternate male mating strategies

1) strategies that convey unequal benefits

a) scorpionfly

b) satellite males

c) female mimicry

d) male coalitions

2) strategies that convey equal benefits

a) gray seal

b) sponge isopod

B. Epigamic Selection: Female mate choice

1. mate choice based on material benefits

a. food

1) hangingflies

2) spermatophore

3) male’s body

b. territory

c. male parental care

1) 15-spined stickleback

2) sedge warbler

3) blue Tit

4) weaver bird

2. mate choice without material benefits

a. choice based on traits that reflect male genetic quality

1) healthy male hypothesis

2) good genes hypothesis

a) ringneck pheasant

b) bowerbirds

c) bird song

d) fluctuating asymmetry

3) evolutionary consequences of choice based on genetic quality

a) sexual dimorphism

b) honest signals

b. choice based on male “attractiveness”

1) runaway selection hypothesis

2) chase-away selection hypothesis

C. Epigamic Selection: Male mate choice

1. factors that favor male choice

2. what is choice based on?

a. size

b. virginity

3. evolutionary consequences of male choice

a. decreased sexual dimorphism

b. sex role reversal

1) pipefish and seahorses

2) spermatophore

III. Mating Systems

A. Monogamy

1. female monogamy

2. male monogamy

a. mate assistance hypothesis

b. mate guarding hypothesis (male enforced monogamy)

c. female enforced monogamy

d. female and male enforced monogamy

B. Polygyny

1. female defense polygyny

2. resource defense polygyny

3. scramble competition polygyny

4. lek polygyny

C. Polyandry

1. genetic benefits polyandry

a. fertility insurance hypothesis

b. good genes hypothesis

c. genetic compatibility hypothesis

d. genetic diversity hypothesis

2. material benefit polyandry

D. Polygynandry

E. A mix of mating systems: ex: Dunnock

Evolution of Helping Behavior

I. Altruism

A. Definition

B. Evolutionary routes for helpful behavior

1. “selfish” behavior

2. mutualism

3. reciprocal altruism

4. kin selection

a. coefficient of relatedness (=r)

b. concept of inclusive fitness

c. theoretical model: B_r/C_d > 1/r

C. Example: Alarm calls for terrestrial predators by Belding’s ground squirrels

	Selfish Behavior	Mutualism	Reciprocal Altruism	Kin Selection
No group defense	✔		✔	✔
Callers have increased risk of predation			✔	✔
Females call > males			✔	✔
Females with relatives nearby call > those without	✔			✔
Females with closer non-descendent kin nearby call > those with more distant relatives nearby				✔
Females show kin discrimination				✔

II. Helpers at the Nest (Helpers at the Den)

A. Examples

1. single-pair systems

2. multiple-pair systems

B. Do helpers help?

1. correlation studies

a. problem of colinearity

b. factors contributing to colinearity

2. removal experiments

C. Factors that favor staying and not breeding

1. shortage of territories (habitat saturation hypothesis)

2. cost of independent reproduction

3. shortage of sexual partners

4. summary

D. Benefits of helping (Why help if you stay?)

1. gain maturity and experience

2. inheritance of parental territory

3. reciprocal altruism

a. coalitions for territorial defense

b. coalitions for care of young

4. parental manipulation

5. increased inclusive fitness

E. Costs and Benefits of Helping at the Nest: Alternate strategies

ex: Pied Kingfisher

	1^o helper	2^o helper
Related to breeding pair?	yes	no
No. breeding pairs helped	1 (parents)	1+
Extra young produced by helped pair	1.8	1.3
Kcal delivered by helper/day	76	18
Treated aggressively by breeding male	no	yes
Probability of surviving to 2nd year	0.54	0.74
Probability of getting mate in 2nd year	0.6	0.91 (helped female)
Relatedness of helper to young	0.32	0.0
Inclusive fitness (year 1 + year 2)	0.99	0.84

Evolution of Helping Behavior: Social Insects and the Evolution of Sterility

I. Characteristics of Social Insects

A. Cooperative brood care

B. Overlap of generations

C. Reproductive division of labor with sterile workers

II. Levels of sociality (Hymenoptera; Isoptera)

A. solitary ancestor

B. primitively social

C. highly social (eusocial)

III. Factors favoring the evolution of eusociality in insects

A. Intrinsic factors

1. haplodiploidy

2. philopatry

3. internal symbionts

B. Extrinsic factors

1. the nest

2. nest predation and nest parasitism

IV. Hypotheses for the evolution of eusociality

A. Kin selection (Haplodiploid Hypothesis)

B. Mutualism and Reciprocity Hypotheses

C. Colony-level selection hypothesis